The present invention relates to a sorter for sorting sheets, which are transferred from a sheet processor, to a plurality of sorting trays, more specifically, it relates to a sorter for sorting the sheets through a sorting treatment or grouping treatment to a plurality of stationary sorting trays using a movable distributing means.
Conventionally, it is well known a sorter which includes an endless belt which are wound between upper and lower pulleys and by which sheets are sequentially fed downward in a vertical direction, a plurality of stationary sorting trays which are arranged along the endless belt and on which sheets are received, and a distributing unit which are movable vertically and provided for distributing the sheet fed by the endless belt to a predetermined sorting tray.
In the conventional sorter, the distributing unit is set to be moved along the endless belt in a condition where it is always remote from the endless belt by a predetermined very small gap. On the other hand, it is necessary to contact the sheet with the outer surface of the endless belt by a predetermined frictional engagement in order to stably feed the sheet in accordance with the running of the endless belt. Accordingly, a several constructions for contacting the sheet with the endless belt are proposed.
Theoretically, it is best to provide a plurality of rollers which are arranged in the vertical direction and always rolling-contacting the outer surface of the endless belt so that the sheet is clamped between the roller and the endless belt whereby the sheet is forcibly engaged with the endless belt by the roller. However, it is impossible to provide the plurality of rollers because the distributing unit must also be moved in the vertical direction and set to be in the closed position relative to the endless belt. That is to say, the rollers and the distributing unit are interfered with each other at the vertical movement of the distributing unit.
As conventional example which is disclosed in U.S. Pat. No. 4,408,756 to Miyashita et al., as shown in FIG. 1, a sorter 100 includes a vacuum case 102 which is arranged in an inner area of the endless belt 104 in such a manner that the opened surface of the vacuum case 102 is contacted with the inner surface of the endless belt 102 on the side where the distributing unit is arranged, and an air suction fan 106 is attached to the vacuum case 102 for causing the inner pressure of the vacuum case 102 be negative, while a multiple small holes (not shown) are formed to the endless belt 104 over the total length thereof. By constructing as described above, the sheet is sucked onto the outer surface of the endless belt 104, whereby the sheet is fed in accordance with the running of the endless belt 104.
However, in the conventional sorter 100 shown in FIG. 1, the construction of the sorter is more complicated and cost thereof is relative high as well as the suction noise from the vacuum case will arise to disturb the office environment. Furthermore, it is very difficult to peel the sheet from the endless belt because the all area of the sheet is closely contacted with or attached to the outer surface of the endless belt 104.